The present invention relates to a semiconductor laser apparatus.
Recently, a semiconductor laser apparatus which irradiates the surface of an optical disk with a laser beam is widely used in a DVD (Digital Versatile Disc) system and the like. FIGS. 4A to 4C illustrate the arrangement of a conventional semiconductor laser apparatus. FIG. 4A is a plan view showing the apparatus. FIG. 4B is a longitudinal sectional view taken along a line C—C in FIG. 4A. FIG. 4C is a left side view.
A semiconductor laser element 103 is mounted on a substrate 105 which is made of silicon or the like and on which a semiconductor laser element mounting bed and a light receiving element 104 are formed. This semiconductor laser element 103 emits a main laser beam 108 forward (to the left in FIG. 4A), and emits a monitoring beam 109 backward. The light receiving element 104 formed in the surface of the substrate 105 receives this monitoring beam 109.
The semiconductor laser element 103 is connected to a lead frame 101 by a bonding wire 107a. The light receiving element 104 is connected to a lead 101a separated from the lead frame 101 by a bonding wire 107b. The substrate 105 is connected to a lead 101b by a bonding wire 107c. 
In addition, an enclosure 102 made of a material such as resin is formed on the lead frame 101 so as to surround the rear portion and two side portions of the semiconductor laser element 103. An enclosure 102a is formed on the lower surface of the lead frame 101.
This semiconductor laser apparatus is installed in a hole formed in a holder of a pickup head (not shown). In this installation, a front section 201 of the lead frame 101 functions as a reference surface for positioning in the forward or backward direction of the main laser beam 108 (in the horizontal direction in FIG. 4A), and side sections 202 function as reference surfaces for positioning in the lateral direction (in the vertical direction in FIG. 4A).
Unfortunately, the above apparatus has the following problem. When the semiconductor laser apparatus is installed in the holder of the pickup head, the relative positional relationship between the semiconductor laser element 103 and the holder is important. That is, the front section 201 as the reference in the forward or backward direction of the main laser beam 108 and the semiconductor laser element 103 are in substantially the same position as shown in FIG. 4A. Therefore, the relative positional relationship between them is unconditionally determined, so the degree of freedom of design is very low. This degree of freedom of design may be increased by moving the semiconductor laser element 103 backward (to the right in FIG. 4A) as needed. However, this increases the dimension in the forward or backward direction of the entire apparatus and hence increases the size of the apparatus, so it is undesirable to use this method.